Apparatus for the separation of solid materials of different specific gravities



Nov. 30, 1937. G. RAW 2,100,670

APPARATUS FOR THE SEPARATION OF SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES 2 Sheets-Sheet l Filed Nov. 18, 1952 Nov. 30, 1937.

G. RAW APPARATUS FOR THE SEPARATION OF SOLID MATERIALS OF DIFFERENT SPECIFIC GRAVITIES Filed NOV. 18, 1932 2 Sheets-Sheet 2 Patented Nov. 30, 1937 UNITED STATES amorp- PATENT OFFIC CIFIC GRAVITIES George Raw, Ravenswood, Low Fell, England Application November 18, 1932, Serial No. 643,258 In Great Britain November 18, 1931 Claims. (Cl. 209-468) This invention comprises improvements in or relating to apparatus for the separation of solid materials of different specific gravities and while intended particularly for application to'the cleaning of coal from stone or dirt or other impurities may be used in other cases where segregation of divided solid components of different densities is desired, as for example in the separation of ores from their gangue.

The invention is concerned with systems in which the materials are subjected to treatment upon forwardly contracted pervious tables or decks associated with pneumatic chambers supplied with pressure of air or other gaseous fluid from a fan or blower to cause the less dense material to stratify above the material of greater density, and the principal objects of the invention are to increase the capacity of the plant for a given size of table or deck unit, to improve the progression of the stratum of denser material along the tables or decks and thus render the separation more rapid and complete, to reduce the power consumption of the plant and finally to lessen materially the initial cost of the installation.

According to this invention, a pneumatic separating table or deck unit, for use in the separation of solid materials of different specific gravities, comprises a plurality of separating tables or decks of similar forwardly contracted form arranged in parallel fashion relatively to the length of the wait, and the different tables or decks are provided with independent pneumatic chambers subjected to pulsations of pressure operating in alternation or sequence in the different chambers. By the use of two or more of such separating tables or decks on a single table chassis of any given size, the separation of the materials can be speeded up and more materials treated so that increased capacity of the plant is obtainable, and by the use of the independent pneumatic chambers, in conjunction with alternately or sequentially operating pulsator mechanism, the output of the fan or blower can be used continuously and none wasted on idle periods, whereby decreased power consumption is attainable as will be described.

As a modification and in cases where very high capacity is required of a plant, a plurality of table units may be used each having two or more separating tables or decks as above described, but a common pneumatic chamber for each unit. In this modification, the fan or blower would be connected by suitable ducts to the respective chambers and pulsator devices at the different table units would be arranged to open in alternation or sequence so that again the output of the fan would be continuously used and none wasted.

A somewhat similar modification also comprises a plurality of table units but there are independent pneumatic chambers for the tables or decks of each unit. The pulsators in this case would operate similarly to the first-mentioned case and very even use of the output of the fan or blower is attainable.

The provision of two or more tables or decks on one chassis in each case enables the capacity of the table units to be increased. In forwardly converging types of table the degree of contrac: tion of the width is less than would be required for maintaining uniform depth of material of the bed in a single table having a width equal to the combined widths of the two or more tables, and a length substantially equal thereto so that progression of the stratum of denser material, as a whole, along the table is facilitated and correspondingly more rapid and complete separation attained. Single tables having such a high degree of contraction are unsatisfactory in operation due to resistance to forward movement by the contractions and crowding of the heavy material at the sides making non-uniformity in the composition of the bed. Single units of increased capacity are cheaper to construct than several separate units and the ability to use the output of the fan in continuous fashion to supply a plurality of pneumatic chambers, results in greatly reduced power consumption for the whole plant with the consequent saving in the cost of mechanical drives and other parts so that on the whole the initial cost of an installation can be considerably reduced.

, The invention comprises improvements which are of advantageous application in connection with the inventions forming the subject of my prior Patents Nos. 1,843,405, 1,730,947 and 1,811,026 and patent application number of even date herewith and BritishPatent No. 336,221. The table or deck units comprising two or more separating portions are of favourable use in the separation of solid materials by operation of static pneumatic pressure conditions according to Patents Nos. 1,843,405 and 1,811,026 as also is the arrangement of independent pneumatic chambers and alternately or sequentially operating pulsators.

In order to enable the invention to be readily understood reference is directed to the accompanying drawings in which:-

Figure 1 is a side elevation illustrative of one 2 form of table or deck unit in accordance with this invention.

Figure 2 or blower.

Figure 3 is a cross-section of Figure 1 taken near the pulsator end of the table unit.

Figure 4 is a plan view of a part of one of the tables or decks in the neighbourhood of a contraction thereof, to illustrate advantageous details of construction.

Figure 5 is a central longitudinal section of Figure 4.

Figure 6 is a section of the pervious table bottom on the line VI-VI of Figure 4.

Figure '7 is a diagrammatic plan view of a modified form of apparatus according to the invention.

Figure 8 is a similar view of another modification.

Figure 9 is a plan of a modified arrangement of the tables of the units.

Figures 10 and 11 are horizontal sections of modified forms of air box, and

Figure 12 is a view similar to the upper part of Figure 3, showing a modified form of discharge means between tables.

The apparatus shown in Figures 1 to 6 is particularly intended for use in the separation of coal from impurities. In Figures 1 to 3, the table unit It comprises a single chassis or frame I) carrying two (or there may be more), separating tables or decks c which are disposed parallel one to another and conveniently have a form similar to the table described in the prior patent specification No. 1,730,947 excepting, of course, that they are narrower. The chassis is suspended in suitable manner, as by spring-steel hangers d, for reciprocatory or jigging operation and this may be brought about by means of an eccentric or other device operative on the rod e connected with the rear end of the chassis. There may be two or more contractions of width of the tables, as desired, and at each contraction a skimmer device I is arranged for the discharge of the less dense material, which takes place at the sides of the table unit and also into the central space between the tables themselves. The denser material is discharged at the extreme forward end of the tables over the hingedly adjustable chutes 9. These discharge devices are of similar nature to those described in my prior patent specifications and therefore need no further description. The materials for separation are fed on to the tables across the whole width of the rear ends thereof by a suitable feed device or devices (not shown) and hoppers or chutes such as h are provided to receive the discharged separated materials.

The single chassis b enables both or all the tables to be reciprocated by a single jigging mechanism as will be apparent. The chassis is arranged over an air box It and connected to the upper edges thereof by flexible couplings l, and this box is divided longitudinally by one, or more, partitions m with flexible couplings n to provide a separate pneumatic chamber 0 for each of the several parallel tables. The construction is preferably such that the individual chambers o are of substantially rectangular section transversely and longitudinally.

Air under pressure is supplied to the table by a single centrifugal fan or blower 10 connected with the rear end of the air box by a flaring duct r and admission of air to the pneumatic chambers of the several tables is controlled by a vertically disposed pulsator device 8 adapted to allow admission of air in sequence to the chambers 0 is a plan of Figure 1, omitting the fan The pulsator is advantageously of the multiple rotary vane construction described in my patent specification No. 1,811,026 but each vane is con structed so that one half t is displaced at rightangles to the other half u in side view, assuming the table unit to comprise two tables or decks. If there were three tables, the vanes would be in three portions arranged at to one another. By this construction of pulsator, admission of air or other gaseous medium to the pneumatic chambers o of the several tables is in alternation or sequence so that pneumatic pressure fluctuations will be caused to occur alternately or sequentially in the respective chambers. It will also be understood that although the pulsator opens and shuts in its respective parts to cause pressure fiuctuations, the load on the fan p is practically uniform because it discharges first into one chamber 0 and then into the other, or the next one and so on if there be more than two chambers, so that in effect the fan discharges continuously. There is thus no fully closed-port period for the fan as is the case with earlier table units using a fan to supply a single pneumatic chamber. When a fan is caused to work against a single-type pulsator, it must deliver all the air that the table requires during the open-port period of the cycle. The closed-port period is wasted and the fan must therefore be of nearly double duty capacity or more according to the duration of the open-port period. A greater pressure is also usually required to be generated by the fan with a singletype pulsator as, due to air inertia and reaction caused by the fully closed port, the full effect of the pressure in generating fluctuations in the air chamber is not obtained. This adverse effect is eliminated with the multiple construction of pulsator which permits of even fan loading. In the present apparatus, the wasted power of the closed port period is utilized for working one or other portion of the table unit and the size of the fan can be reduced as compared with that required for a single-table unit of the earlier type of similar proportions, for example for a two-table unit the size of the fan can be reduced by nearly half, because the duty of the fan is equivalent to one half only of the table unit. It follows, therefore, that the power consumption of the fan is approximately only half that of the earlier table unit and similarly with table units comprising more than two tables or decks. It is particularly to be noted that these advantages are obtained on a single table unit. By the present invention, the power reduction may be secured for each individual machine and it is not necessary to use two complete units to give uniform fan load, this being an advantage where two complete separating machines are not always required. The halves or parts it, u, of the pulsator vanes would be separated by disc portions coincident with the air box partition m, and though omitted for sake of clearness in the more or less diagrammatic representation of the pulsator in the drawings, sealing pieces would be provided between the vanes (of. parts 2 in my patent specification No. 1,811,026) in order to ensure a period of fully shut port for each individual pneumatic chamber 0. The vanes may be rotated by any suitable gearing from the shaft 0 such as by bevel gearing as described in the said patent specification and the reference letter 10 in Figure 3 shows the casing for this gearing.

It may be noted that any of the forwardly converging types of tables may be used in carrying out the invention. Preferably, the table chassis is slightly inclined forwardly and downwardly Cir in use but the inclination may be varied according to circumstances. The less dense material or coal which is discharged by the Skimmers f into the central space between the tables may be conveyed to the forward end under the reciprocatory action of the chassis and there fall into a hopper or hoppers, or a trough or troughs 1 may be mounted on the chassis within this space as shown in Figure 12 and slightly inclined forwardly and downwardly to a hopper or hoppers at the forward end. Or, as another alternative, and as shown in Figure 10, the air box It between the table portions, may have two partitions m spaced apart to form a gap through which the less dense material may discharge to collecting means such as hoppers like the hoppers h shown at the sides of the table-unit in Figures 1 and 2. Where a double partition arrangement is used to form a discharge gap between the air chambers o, the connections between the partitions and the pulsator would be suitably designed to prevent the entrance of air into the central gap, i. e. the gap would be sealed across in front of the centre of the pulsator, e. g., the central discs of the pulsator vanes may be made as broad as the gap between the partitions 'm. so that this width is sealed to the air. The connecting ends of the partitions would then be shaped to fit closely round the central discs. Alternatively, a solid central casing part to which the partitions 111 would be connected, may be provided in the pulsator to coincide with the gap between partitions m. The two halves of each vane would then pass through holes in the solid casing part which blanks off the gap. Suitable bearings may be fitted in the casing if desired, to provide central support for the vanes. Two further arrangements are shown in Figures 10 and 11. In Figure 10 the dotted lines at m indicate that the central gap between the partitions 11:. need only extend from the point of first discharge, i. e. the first skimmer 7, to the forward end of the air box. In Figure 11 the gaps are shown localized only at the actual points of discharge, i. e. at the positions of the several skimmers f and take the form of vertical chutes m passing through the air box 70.

As regards the individual tables or decks, it is of advantage to give the upstanding sides a gently curved form in plan in the neighbourhood of the contractions, as shown for instance at I inFigures 2 and 4, in order to facilitate movement of the denser material, instead of making the contractions sharply angular. The forward and downward slopes 2, in the bottom of the tables, may also be advantageously modified, as seen in Figures 2 and 4, so that while the top edges of the slopes follow the shape of the vertical walls of the skimmers f in plan, the base edges are curved inwardly in such a manner that the slopes, which are preferably imperforate, are very narrow at the sides and broad at the centre. The efi'ect of this is to make these slopes of very sharp declination at the sides and very much less steep in the centre as will be apparent from Figures and 6. Any tendency of the denser material to accumulate and thus cause squeeze or discharge thereof over the sides of the contractions, is negatived by the much steeper slope over which it flows there and the rate of progression of the denser stratum is caused to be much more uniform across the width of the table. Also, the skimmers f can now be set over the contractions of the table, instead of before them, because of the greater freedom of movement of the material, thusen'abling the length of the table to be reduced. These improvements add materially to the capacity of the table and contribute to a more complete separating action. The im-- perforate slopes 2 suitably start slightly beyond the vertical'walls of the skimmers, as shown, to prevent any possible breakage of the continuity of the bed before the shimmers 1 have completely separated the strata, a narrow horizontal imperfo'rate part 3 extending slightly under the horizontal perforate foot part of the skimmers, as seen in Figure 5, to prevent undue air leakage through the bed at the slopes.

According to the modified form of apparatus illustrated in Figure 7, two table-units 4, 4 with multiple tables or decks c, as described, are employed, but each table-unit has a common pneumatic chamber or air box. The chambers are connected to a common fan or blower 5, by sultably branched air ducting 6, and a multiple rotary vane pulsator of the kind described in my patent specification No. 1,311,026 aforesaid, is applied at the rear of the pneumatic chamber of each table-unit. The pulsator 7 of one unit would be set so as to present open ports while the pulsator 8 of the other unit is presenting closed ports and vice versa, as indicated by the diagrammatic showing of the vanes in the draw ings, and in this way alternate operation of the table-units is possible similarly to the first-described arrangement.

The modification illustrated by Figure 8 is somewhat similar to Figure 7 and similar parts are similarly numbered, but in this case the tableunits 9 have the same construction as described with reference to Figures 1 to 3, the air boxes of the units being divided by partitions m and having pulsators of similar form to that shown in Figures 1 and 3. There is thus always an open-port period in each of the branches 6 from the fan or blower 5 and very even use of the output of the fan or blower is possible.

The multiple-unit constructions illustrated by Figures '7 and 8 are intended for use in cases where more than one separating machine is required in order to secure a very high capacity. Multiple-unit arrangements may also be used which comprise more than two units as will be understood, the pulsators being set accordingly.

Figure 9 of the drawings illustrates a modification in which the tables a are placed close together on the chassis. This arrangement reduces the overall width and weight of the unit. This construction may be adopted in the case of some coals and particularly when treating a coal which is uniform in character and when a single feeding device may be used across the whole width of the two tables. If desired, and particularly when the several tables of any unit are operated with a common pneumatic chamber, as in Figure 7 for example, the central upstanding table partition at I I may be omitted, so that the tables are merged in one at the feed end and division of the unit into separate tables only occurs from the point where the first skimmers are placed. In both of these cases the central discharge gap is formed solely by the inside contractions of the two decks. Suitable discharges may still be provided through the air box, e. g. Figure 10 (dotted arrangement) and Figure 11, whether a single chamber or separate chamber be used, the central divisional partition parts being dispensed with in the former case, and only the parts used which form the discharge chutes. Alternatively the central discharge may be, as before described, carried to the forward end of the table, by the reciprocatory movement of the table. There may be separate feed devices for the tables or a common feed device may be used.

In all constructions, it will be seen that if very large table-units are required, a greater feed width is obtainable than with earlier types employing spaced contractions. In the latter, the maximum width is largely governed by the extent of the contractions necessary in passing from one part of the table to another, as these tend to hold up the progression of the denser material. In the improved tables, the degree of contraction is much reduced, as the contractions are spread over the two or more tables. Consequently, tables of greater capacitycan be built and satisfactorily operated.

Finally, the ability to treat a given quantity of material on one separating unit, instead of using two or more, means in addition to the advantages described, a very great saving in capital cost, as not only is the one unit cheaper to construct than two or more units, but the proportions of the necessary supporting and housing structure are greatly reduced. Furthermore, the mechanical control of the tables is simplified and therefore less supervision is required, while in most cases the conveyors, elevators and other parts necessary for the supply and collection of the materials are simplified and thus reduced in cost.

I claim:--

1. Apparatus for the separation of materials of different specific gravities comprising a permeable table or deck unit having a single frame or chassis, means for jigging said unit, a blower, control means for supplying sharp pneumatic pressure variations to said unit, said control means including sealing pieces for providing alternate periods of fully interrupted supply of pneumatic pressure to increase the rate of stratification of the materials and minimize the necessary length of travel of the materials on the deck unit, means for removing the flotant stratum of material from the unit substantially at the rate said stratum is formed, said removing means comprising a plurality of pairs of generally forwardly converging side walls dividing the deck unit into a plurality of decks disposed side by side, said side walls having forwardly spaced contracted portions and substantially parallel portions, and means at the contracted portions for guiding the flotant stratum over the side walls, the total amount of contraction of all the side walls being suflicient to compensate for the discharge of the flotant stratum of material from the deck as formed and preserve uniformity of depth of the bed of material, the said total amount of contraction of the unit being divided among the side Walls so that the degree of contraction of each wall is sufiiciently low so as not to interfere with the forward movement of the material on the decks, and said decks being free of projections extending into the path of the material.

2. Apparatus in accordance with claim 1, wherein the contractions of the sides of the tables or decks are of gently curved form in plan.

3. Apparatus in accordance with claim 1, wherein the means for guiding the flotant stratum over the side walls comprises skimmers of V form in plan and the bottoms of said tables or decks are formed with forwardly and downwardly extending sloping parts of which the upper edge conforms substantially to the shape of the adjacent skimmers in plan and the lower edge is curved inwardly so that the slopes are narrow and steep at the sides of said tables or decks and very broad with slight inclination at the longitudinal center line of said tables or decks.

4. Apparatus according to claim 1 and discharge trough means extending longitudinally of said unit in the space between said tables or decks and widening forwardly in correspondence with the contracted form of the tables or decks, said trough means being carried by said chassis so as to be shaken therewith and carrying the discharged upper stratum towards the forward end of said unit.

5. Apparatus according to claim 1, in which the table or deck of the unit is merged in one at the rear end and the side Walls separate the deck into a plurality of paths from the point where the first discharge takes place over the sides of the table or deck.

GEORGE RAW. 

